POJ 2653 Pick-up sticks 线段相交

题目大意：一次丢下去n根木棒，问那些木棒不被其他木棒压着，依次输出。

题目思路：叉积判断线段是否相交，吐槽下POJ数据真弱竟然没超时……

#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<vector>
#include<queue>
#define INF 0x3f3f3f3f
#define MAX 100005

struct node
{
    double x1,y1,x2,y2;
}point[MAX];

int vis[MAX],n;

double Cross(double x1,double y1,double x2,double y2,double x3,double y3,double x4,double y4)
{
    double a=(x2-x1)*(y3-y1)-(x3-x1)*(y2-y1);
    double b=(x2-x1)*(y4-y1)-(x4-x1)*(y2-y1);
    return a*b;
}

void Solve()
{
    for(int i=1;i<n;i++)
    {
        double x1=point[i].x1;
        double y1=point[i].y1;
        double x2=point[i].x2;
        double y2=point[i].y2;
        for(int j=i+1;j<=n;j++)
        {
            if(Cross(x1,y1,x2,y2,point[j].x1,point[j].y1,point[j].x2,point[j].y2)<=1e-10 && Cross(point[j].x1,point[j].y1,point[j].x2,point[j].y2,x1,y1,x2,y2)<=1e-10)
            {
                vis[i]=1;
                break;
            }
        }
    }
    printf("Top sticks: ");
    for(int i=1;i<n;i++)
    {
        if(!vis[i])
            printf("%d, ",i);
    }
    printf("%d.
",n);
}

int main()
{
    while(scanf("%d",&n),n)
    {
        for(int i=1;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&point[i].x1,&point[i].y1,&point[i].x2,&point[i].y2);
            vis[i]=0;
        }
        Solve();
    }
    return 0;
}